1. Field of the Invention
The present invention relates to document copying apparatus, and more particularly to means for generating and modifying electrical signals and for applying those signals to an exposure station.
2. Description of the Prior Art
Document copiers which include reader devices for generating electrical signals representative of imagewise information in an original scene and for applying the signals to the controls of an exposure station are known in the prior art. For instance, co-assigned U.S. Pat. No. 3,783,185, which issued to Richard A. Spaulding on Jan. 1, 1974, discloses a laser printer in which a color transparency is scanned and three electrical signals, representative of the color information of the transparency, control the color output of the laser as it scans the print material. However, that patent discloses no means for correcting the signals to correct for characteristics of the original document which would result in inferior prints.
Certain techniques for transformation and enhancement of electrical color signals have been utilized in other environments. For instance, in the television arts it is well known to generate a video signal and to apply certain signal correction techniques thereto. However, heretofore the manner in which such techniques can be advantageously utilized in the document copier field has not been recognized. Also, such known techniques for correcting signals are not directly applicable for utilization in document copiers and improved, more efficient techniques, specifically adapted for the particular purpose of copying documents, are required to allow transformation and enhancement in that environment.